The hood features a unique flow straightener, which significantly improves measurement accuracy, saving you valuable time on difficult tasks
The testo 420 control unit can be tilted for a more convenient view of the display
The included Bluetooth / app feature allows for wireless connection to mobile devices, for remote monitoring, as well as remote operation
The testo 420 app can send measurement reports directly from the work site via email
For additional convenience, there is an optional tripod when working with high ceilings, as well as four additional flow hood sizes available for complete versatility
The testo 420 is also a CEC approved air flow capture hood
Temperature - NTC
Measuring range -4° to 158 °F / -20 to +70 °C
Accuracy ±1 °F (32° to 158 °F) / ±0.5 °C (0 to +70 °C) ±1.4 °F (-4° to 32 °F) / ±0.8 °C (-20 to +0 °C)
Resolution 0.1 °F / 0.1 °C
Reaction time 45 sec (t90)
Humidity - Capacitive
Measuring range 0 to 100 %rH
Accuracy ±1.8 %rH + 3 % of mv at +77 °F / ±1.8 %RH + 3 % of mv at +25 °C (5 to 80 %rH)
Resolution 0.1 %rH
Differential Pressure
Measuring range -0.480 to 0.480 InH₂O / -120 to +120 Pa
Accuracy ±2 % of mv + 0.002 InH₂O at +72 °F, 405 InH₂O / ±2 % of mv + 0.5 Pa at +22 °C, 1013 hPa
Resolution 0.001 InH₂O / 0.001 Pa
Reaction time 1 sec (t90)
Absolute Pressure
Measuring range 280 to 440 InH₂O / 700 to 1100 hPa
Accuracy ±1 InH₂O / ±3 hPa
Resolution 0.1 InH₂O / 0.1 hPa
Reaction time 1 sec
Volume flow
Measuring range 24 to 2354 CFM / 40 to 4000 m³/h
Accuracy ±3 % of mv + 7 CFM at +72 °F / ±3 % of mv + 12 m³/h at +22 °C 405 InH₂O (50 to 2060 CFM) / 1013 hPa (85 to 3500 m³/h)
Resolution 1 CFM / 1 m³/h
Reaction time 1 sec (t90)
Dimensions 24 x 24 in. (Standard hood) / 610 x 610 mm (Standard hood)
Operating temperature 23° to 122 °F / -5 to +50 °C